Examples of such a currently-used apparatus include an apparatus as under. That is, the apparatus is provided with a printing head with a plurality of inkjet heads, a cap unit, and wiper blades. The cap unit moves between a capping position where nozzles of the inkjet heads are each closed and a retracting position where the nozzles are opened in a direction orthogonal to a direction where the inkjet heads are arranged. The wiper blades move in the direction where the inkjet heads are arranged when the cap unit is in the retracting position, thereby wiping the nozzles individually. See, for example, Japanese Patent Publication No. 2012-157989A.
The inkjet printing apparatus performs printing on a printing sheet by discharging ink droplets. Such an inkjet printing apparatus typically performs purge periodically by sucking or pressurizing all the nozzles of the printing head in order not to generate any undischarged nozzles from thickened ink droplets having enhanced viscosity. Accordingly, ink droplets accumulate on discharge faces of the printing head with outlets of all the nozzles being opened. Then the cap unit wipes the discharge faces of the printing head in its retracting position using the wiper blades. This achieves removal of the ink droplets accumulating on the discharge faces of the printing head.
On the other hand, the purge causes dispersion of the ink droplets within the cap unit. As a result, the ink droplets adhere on an inner peripheral edge of the cap unit. Accordingly, movement of the cap unit into the capping position leads to transfer of the ink droplets on a top face of the cap unit with enhanced viscosity to the discharge faces of the inkjet heads. Such transfer causes the ink droplets to be left on the discharge face of the printing head with asperities if the ink droplets continuously remain as cap impressions of the cap unit. Accordingly, uneven cleaning occurs upon wiper of the discharge face with the wiper blades. Such a drawback may arise.
Then, an apparatus has been suggested that includes a cap unit and a cleaning unit. The cap unit is disposed below a printing head and a transport path on which a printing sheet is transported. The cleaning unit is disposed between a top face of the cap unit and the transport path and is spaced away from the cap unit. See, for example, Japanese Patent No. 5180878A.
The apparatus includes the cleaning unit having lips. The lips project toward the top face of the cap unit, and lower ends thereof are each lower in level than the top face of the cap unit. When the cleaning unit is moved horizontally while the printing sheet is fed out of the transport path, the lips slide over the top face of the cap unit. Accordingly, the ink droplets on the top face of the cap unit are wiped off. Then, the cap unit is moved upward to the capping position to close the discharge faces of the printing head. Here, the top face of the cap unit is cleaned by the cleaning unit. Consequently, the discharge faces of the printing head have resistance to contamination due to the ink droplet transfer from the cap unit. This causes less cleaning unevenness.
However, the examples of the conventional apparatus with such configurations as above have the following drawbacks.
Specifically, the lips of the currently-used apparatus projecting below the top face of the cap unit slide on the top face of the cap unit. Accordingly, the top face of the cap unit becomes worn and damaged. Such a drawback may arise. In addition, the cleaning unit is spaced away from the top face of the cap unit. This leads to the dried inside of the cap unit. Consequently, the dried inside of the cap unit due to exposure to air prevents moisture retention of the nozzles upon movement of the cap unit to the capping position. Accordingly, this produces the ink droplets with the enhanced viscosity on the discharge faces of the printing head, whereby some undischarged nozzles are generated. Such a drawback may also arise.